The meaning of "High TG" in high TG boards

The circuit board must be not flammable, cannot burn at a certain temperature, and can only be softened. The temperature point at this time is called the glass transition temperature (TG point), and this value is related to the dimensional stability of the PCB board.

The critical temperature at which the CCL is melted by the solid state into a rubbery fluid, called the TG point, also called the melting point. The higher the TG point, the higher the temperature requirement when pressing core, and the pressed out boards will be harder and more brittle, which will affect the quality of the next process mechanical drilling (if any) and the electrical characteristics when used.

The TG point is the maximum temperature (° C.) at which the CCL remains rigid. That is to say, ordinary PCB CCL materials not only produce softening, deformation, melting, etc. at high temperatures, but also show a sharp decline in mechanical and electrical properties. General TG CCL is more than 130 degrees, High-TG is generally greater than 170 degrees, and medium TG is greater than about 150 degrees. The TG of the CCL is increased, the thermal resistance, moisture resistance, chemical resistance, stability, etc. of the printed board features will improve. The higher the TG value, the better the temperature resistance of the CCL, especially in the hot air solder level lead-free process, the application of high TG is more. Therefore, the higher the TG value in the high TG circuit board, the better the PCB temperature resistance.

The difference between the general FR-4 and the high TG FR-4 is: in the hot state, especially when heated under moisture absorption, differences in the mechanical strength of its material, dimensionally stability, adhesion, absorbent, thermally decomposable, thermal expansion, etc., and high TG products are significantly better than ordinary PCB CCL materials.